1. Field of the Invention
The present invention relates to a surface treatment method for a polyester film and, more particularly, to a method for treating a surface of a polyester film to eliminate stickiness on the surface of a polyester film which exhibits such stickiness after having been heated.
2. Description of the Prior Art
A polyester film, that is, a thermoplastic polyester film, a typical example of which is a polyethylene terephthalate film, is widely adopted as base film for magnetic tape. In the manufacture of such magnetic tape, a metallic thin film (magnetic material) is formed on one surface of a polyester film by vapor deposition, sputtering or the like. Due to the heat applied during formation of such a metallic thin film, the other surface of the polyester film on which the metallic thin film is not formed is rendered sticky. One of the important properties of magnetic tape is good travel characteristics. However, when the surface of such a polyester film as a base film becomes sticky, the coefficient of friction increases to significantly impair the travel characteristics of the tape.
It has been conventionally proposed to apply a coating agent such as a polymeric material so as to eliminate such stickiness on the surface of a polyester film due to having undergone heating.
When a magnetic tape having a film of a coating agent on its rear surface is assembled in a tape cassette and is made to travel, it is brought into constant contact with pads of the tape cassette, causing the problem of peel-off (dusting) of the film. Magnetic tape from which the film has become peeled off cannot travel stably.